bon, hydrogen, and oxygen, forming that class of tissues represented by the gluten in wheat, the white of an egg, muscular and tendinous fibers, etc.
Ether Extract.—Under this term is included the fats and oils, the term fat being applied to animal fat and the term oil to vegetable products. These bodies are all soluble in ether and therefore are grouped together under the term "ether extract." There are some fats both in animal and vegetable substances insoluble in ether, but they exist in minute quantities and therefore are not separated from the extracts, but the whole matter is given together and represents practically the fats and oils in food.
There are also minute quantities of bodies not fats in foods soluble in ether, and these are included in the ether extract.
Ash.—The term ash is applied to the residue left after the burning of food products in the air at a low temperature until the carbon has disappeared. Ash is rather an indefinite term and is applied to that residual material of a mineral nature composed of sand or silica and the carbonates or oxids of alkaline earth or alkalies. The ash also contains the principal part of phosphorus present in food products and usually a small proportion of sulfur. These bodies in the ash exist as phosphoric and sulfuric acids or their salts.
Fiber.—The term fiber is applied to those carbohydrate products in food which are insoluble in solutions of dilute acid and dilute alkalies at the boiling temperature. Inasmuch as these separated bodies are not wholly pure cellulose they are often designated as crude fiber.
Starch and Sugar.—The terms starch and sugar are applied to the carbohydrates in a food product of a starchy or saccharine nature, together with the other carbohydrates present which are soluble in dilute acids and alkalies.
Calories.—The term calorie is used to denote the amount of heat-forming material contained in one unit weight of a food product. The number given represents the number of degrees of temperature produced in a unit mass of water by the heat formed in burning the unit weight of food. The unit weights employed are usually as follows: Of the food product, one gram (15 grains); unit weight of water to be heated, one kilogram (2.2 pounds); unit increment of temperature, 1°C. (1.8°F.). The expression 4000 calories therefore means that if one gram of food substance in a dry state be burned the heat produced will raise one gram of water through a temperature of 4000°C., or the unit of water (one kilogram) through a temperature of 4°C. For convenience the calories are usually expressed as small calories, namely 4000, instead of large calories, namely 4. In this manual the expression in terms of small calories, that is, the temperature increase of one kilogram of water produced by burning one gram of substance, multiplied by 1000, will be uniformly employed.
